Hypersensitivity Reactions

Question 1

Type 1
Type
Immune mechanism
Mechanism of tissue injury
Example

Answer 1

Type: Immediate
Immune mechanism: Preformed IgE
Mechanism of tissue injury: Mast cells release histamine (immediate) and leukotriene (delayed).
Examples: Anaphylactic and atopic like bees, drugs, allergies

Question 2

Type 2
Type
Immune mechanism
Mechanism of tissue injury

Answer 2

Type: Cytotoxic
Immune mechanism: Ab to Antigens on enemy cells
Mechanism of tissue injury: Antibody and complement –> MAC
Examples: Specific to a tissue site, like autoimmune hemolytic anemia, pemphigus, rheumatic fever.

Question 3

Type 3
Type
Immune mechanism
Mechanism of tissue injury
Example

Answer 3

Type: Immune complex mediated
Immune mechanism: Antibodies binds antigens which activate complement
Mechanism of tissue injury: Complement recruits neutrophils which release lysosomal enzymes
Example: SLE, PN, Post-strep GN, Serum sickness, Arthrus reaction (tetanus and diptheria boosters)

Question 4

Type 4
Type
Immune mechanism
Mechanism of tissue injury
Example

Answer 4

Type: Delayed type
Immune mechanism: Sensitized T cells encounter Ag and secrete lymphokines
Mechanism of tissue injury: Lymphokines (IFN-y) activate macrophages (no Abs involved)
Example: Transplant, Touching (contact dermatitis), TB tests (PPD).

Question 5

Toxic shock syndrome mediators?

Answer 5

IL1, IL6, and TNFa from macrophages and IFNy from T cells.